Instrument for measuring the curvature of the cornea



July 18, 1933. H. HARTINGER 1,918,540

" INSTRUMENT FOR MEASURING THE CURVATURE OF 155 CORNEA Filed March 12, 1931 2 Sheets-Sheet l Fig. 5 Fig. 6

Inventor:

July 18, 1933. 'H.I-;IARTINGER 1,918,540

INSTRUMENT F'OR MEASURINGTHE CURVATURE OF THE CORNEA Filed March 12, 1951 2 Sheets-Sheet 2 Patented July 18 1933 t J BN Q E ;I

ms or mutual-ma liasvma 'rn'n inivan or; U i mammalian .4m,wa ting,an is Y 51 have :filed n application iii; ,Ginany,

' March 13, 1930, of j which the following as a specification:

With the ophtnalmometers used 1- in oculi'st 5 racticethe radius of -curvature of vthejsur measuredjfby ,soh-fit'is, advisable to use e uimamrs; which ace of the cornea, isg'ener'ally- I I optically determining the size of the reflected image of an illum'inated 'or transilluminated test object of knowndimensions produce 7 thecorneal surface. "The living eyetobecx- ,amined and, consequently, also the saidimage "never being motionless prohibits takings. di

, rect measurement with, say, a graduat on pro-,

vided "n the ocular ,focal plane' ofi a micro- 1! J avaleschiotz, use is made iOitWO geometrical \figure's serving as test objects and allowing to be displaced symmetricallyto the axis of the e'yeon a curved uide having its centre. in the corneal'vertex;

of the test figuresthereflectedimages of which are viewed by means a microscope:

In the microscope is inserted -a rism of double refraction which permits to o tain'two images of each test object. That 'osition of the test objects on the curved the one microscopic image f t just touches the p then m"croscopic irna of these test objects I in the sense 0 measuring direction, ing the value of. ture. the measurement changing relatively" to the displacement of the. testobj'ects, the described measuring method is liar as the curvature is measured according to its value in different zones. effected measurement will therefore not'permit to know; at once to whichzone ofthe eye the just found value'refers.

This inconvenience isovercome the pres ent invention. j The new m ethod' consists therein that the eye is offered the view o'f'the' two test objects under an unchangeable angle, that optical-means separate from the imagf observing device "two ing ra pencil of the 'partia rag pencils, andthat'the mutual positions of t 50 jects permit of determining the corneal curvature; '3 The infiue corneal surface isg-velrys tothe infinite distance otth jtest obiectsgthi u d by i t foffthe corneal surface whic scope. i In "the 1 lophthalrnometer; system he length of the test "ohi, ject is the distance between the exterior edges e inwhich h e test objects" fit 0' ,allows I of j-deduc the corneal fl'cui'i'va The cornealselements efiective'uponi',

"f phr g j io iraylpencil withft. axial partial my; pencils, 'Jvvhe'reb'y'v the posij he g b ang s,

disadvantageous in so 1 must be adapte the two test objects and the axis oiftheobtoihfill asjal basis'for the observati n 'q o neal' e displaced imagesof thetest obv l l ss the f v s the "distance of the test objects from the eye 61 "upo t s z o t es fl esv-p d by t influence 1s withoutany efiect. [Forfthis re'a r ,'1 ,testiil it 'i fi can i finit y gre distance; Relatively itsposition that 'zone j mil t- 1 1 5 forv the measf rement dependslonf the position T whi'ch"the :cros'sjsections erthaseparma, i gm' my p n ils have the ota c' f sect on of ima'gin :rays. f This Position b M IPngabIe; 1 w y l ei a e zo e bi. the conneais used for'measuring', In'praetice A it isin most cases advisable to so. deviate both pa i rhyr si n ibppd ti' e l'by a A a Toptical means e'achthat thejijnaggsapear =1 inthe "central part of 'the'field'oi vlejfiio the 10 observingdevice. 5 a v i x I: nstrum 'nt according to the invention is therefore" suitahly'co structed-jas follows The, instrument is connected withitwof tiest objectsf whose position's relative to eachfother "I6 7 and to theobsenving devicecannot bejaltered;

forinstance with two collimatqrs' whose axes liein' on'e'plane withthe axis 'of'theobser ving "de i e ng u hi mah r' that these .ax s, n- "tersect that oithe'jobservingdevice apptoxi so inately in one pointjandunder equalandjlm a iiivthei athfqf e m I ing raysof the observing" evicei's pltqvided P ns do ni h imagin tions of the diaiphragm apertures naturally tatlevp a t iii d-by;

serving device; The sizes and positions of the "apertures; in -'.'thetotal a cross section I of the imaging raysifdetermine the corneal zone upon whichthemeasuringisbased. fllnorder zone 1 concentric to I 95.. apertures late. piefei'abl' arranged oppositely "ejac e axis ofjthe eye, both of vequaji n "tancejs from the axis-of the;tota l{1 aypencil.' It is advisable to v provide in at lea t 0116' of he paths of rays an I optical fldeyiat 10C other at'equal jdisi j ever, in order to facilitate measuring, the 1 a I one of thetest ob ects I is conveniently constructed as a scale lying in the above men.- tioned' plane and the other as an index indicating a point .Off this. plane.- When the said scale has a suitable division the sought value of the corneal curvature is represented" by that point on the scale which is indicated a [by the index. [No mampulation of moving parts being r'equir'edthe measuring. process as well as the constructionof the instrument I lified." Naturally 'the jsc'ale maybe divide asgwell in such a manher that the dioptric power of the cornea is exceedingly sim -Eyes afilicted with astigmatism have, I I

ractive powers .ln

'efi'ect I of the refractive and' the aqueous humor can be read off direct. A mark'serving as a viewing-point and being conveniently pro- .vided at agreatdistance, will in any .case" facilitatemaintaining the patients position required for measuring.

eye in the as is well known, difl'erentre I di'fi'erent, meridional planes {Ithes'ejrefractive powers have extreme values in twoplan'es perpendicular to each other erally termed the principal I For the examination, of such I v ment is conveniently'so constructed that the test .objects are rotatable together; with. thesection I lanes. eyes the lIlStlllw observing device abouttheaxis' of'the same I and, that provision is made of an angle measuring dev ce indicatingthe'value of the turning angles fl Theastigmatism of the eye un j ,der examination is indicated by altitudinal deviation's of the images of the test, objects from the repeatedlv deviations will disappear as soon as this the invention the o servin device,

tion planes. -tion ofthe refractive,

- lows of eingused mentioned plane, which planecoincides with onejof the principal seclar position oftheseprincipal section lanes. Moreover, if two instruments according to are combined .in such a way that they have one common observing deviceywhereby the planes each of which .is

- gether and by the axis "Vice erpendicularly'inter'sect inthe axis of measuring is simplified determined by two test objects belonging toof, the observing dein so far as, or obtaining the values for both principal section planes simultane ously, the.

instrument needs being turned only once. Inand two appertaining in-- sjcase w f's zdices will appear in the field of view of the "microscope. With a view'to avoid any confusion in reading, each of the pairs of' test dially disp 'which'are gen-Y I I I I i'dial direction, the positions of the cross sec- 1 In addition to the .determina powersin the principal section lanesthe instrument therefore al-' also forfinding the angu- "trate the invention, s I ample of an instrument with collimators for objects belonging together may be given another, colour. v

It was stated already that an essential advantage of the new method consists therein that the measuring is based always on the same zone: ofthe' cornea of the eye under exrespondingly; difi'erent distance from the axls of the observing device. In thismam examined phragms. 4

In order to be in a position to continuousl y'Iefi'ect such examinations over the whole corneal surface, the-diaphragm may be conv structe'd forinstance in such a manner that its diaphra m apertures 'permit'of being raaced,f or in' the image plane of the imagingsystemiof the observing device may be disposed an additional diaphragm whose diaphragm apertures are, so arranged that theima es of the "test objects lie in any case within are apertures. If now strips of spherical or cylindrical lenses, which would havefto be rovided immediately in front of e said apertures, are-slid in raor' behind tgraduallybymean's of a set of diations of the separated partial ray pencils fseemfto be altered in the total cross'section of the imaging ra In thiscase is altered the position of t e apertures in the diaphragm separating the partial ray pencils, whic serve as entrance'pupils and are imaged'by the imaging system of the observing device in the reverse ray path approximately ner the whole of thecorneal surface'may be in thetangential plane of the cornea. For

allowing to examine cornea the view ng direction of the eye under examination must be altered relatively to theinstrument. This is achieved in the'mostradially displacing the I simple manner by mark serving asa viewing point. I I

The accompanyin drawings, whichillusowe constructional exmeasurin f the radius of curvature of the cornea; 'igure 1 i s'a'central the instrument in front is aview of the instrument in side elevation. Figures 3 and 4 illustrate a single part of the instrument on anenlarged scale in front and, respectively, insi'de elevation. Figures 5 and 6 represent on'an enlarged'scalethe two condensers" with thetest objects of the 'collimatorswhich lie in the horizontal plane and Figures 7 and.8 the condensers with the testobjects of the collimators lying in the vertical plane. Figures 9, 10, jandill respec tively show on an enlarged scale the single eccentric zonesof the section through elevation. Figure 2 J 1nstrument,in v V symmetrical eye, in the beginning of the a bearing provided in part lying inthe ocular image plane of the the examination of an axially measuring, andafter adjustment to an eye afliicted with astigmatism. c t

The instrument is horizontally mounted in .1 resting ona foot 2 (cf; Figures 1 and 2) and'consists of four collimators and a viewing microscope. The collimators are housings 3 each havin in its end an incandescent bulb4 and a u'g box 5. Behind the bulb 4 is disposed, a con- 'den'serconsisting of two plane concave lenses 6, 6, 6" and, respectively, 6'! plane surfaces 8, 8', 8" and, which are farthest away from the bulbs are provided withone test objectea'ch, Each of the surfaces, 8, 8', 8 and 8"Ilies in the focal lane ofone of the colli'matorlenses 9 disposed at the other end of the collimators. The axes of the collimators, whereof two lie in a horizontal and twoin a vertical plane, inter sect in a point 10 which approximatel" corre- 1 sponds to the position of t i V e centre o curvature of the cornea 11 of an eye to be examined, 12, opposite the instrument. The collim'ators are mounted in a support 13 screwed to the objective end of the viewing microsco e. The

axis of this microscope coincides wit the intersect1on line the two pairs of collimators;

In the objectiveend of the microscope tube,

' 14, is mounted an ob ective 15 and the other end, in an ocular sleeve 17, is inserted a two-lens ocular 16. plane parallel glass late 18 whereof one surface is provided wit four line marks .19 displaced 90 relatively to each other. Between the objective 15 and vided in thecasing of two planeconvex converging 21. The plane surfaceof ures 1, 3 and 4) is covered by a film 22 preventing passage of light. In this film 22 are the ocular 16 is pro provided four quadrilateral apertures 23,. 23'

23" and 23 which are coveredby four re-' fracting prisms/24, 24", 24", 24 inthe manner indicated by Figures 3 and-4.

The housing 14 supports a disc.25 which allows of bein screwed to the earing 1. The disc 25 has a a graduation 27 and on the edge ofthe-discl26 an index 28 is provided. Y a I. a

The test objects of thecollimators lyin in the horizontal plane (Figures 5 and 6 are represented by crosslines' 29 with elongated horizontal line and byfla double division 31, 31 provided ontwo'hori z'ontal and parallel lines 30, and having division .numerals in-mirror script. The arrangement is made in such line of the cross 29 and the centre of thespace between the lines termined by the collimator axes The scales 31 and 31 are graduated to represent theradii of curvature in is a planeparallel glass p1ate' 35.

and 7 whose respectively, 8',

index 28 has pointat the of the planes determined The sleeve 17 holds a' 14 a reversing system lenses 20, helens 20s(cf.. Fig

i as objects forth'efob ectivel5. I r The ocular sl 'eve'17 ndthe defined test markimages' c v a In'the reverse path-of rays the objective, a manner that the horizontal 30, 30 lie in the plane de': 231" on a 'plane'which;

the refractive powers in dioptres. The test objects-provided in the two other collimators (Figure's7 and 8) are arrangedin quite the samejr manner with referen'cetothe vertical planeof the coll'mator axes. These two test objects consist provided on wo parallel lines In the rear focal plane of the objectivelfi a On this glass plate35 the rearlfocus of the objective ,15 is indicated by means of aspotof luminous When using the instrument the observer views the eye 12 by means ofthe' viewing microscope after having lighted descent lamp 4 by connecting the to alight source. The ocular16 o ing 'mlcroscope is then so adjustedthat the observer sees distinctly the lines 19 on the the incanplug box 5 the viewglass plate 18. It is hereby assumedthat the been previously .qadjusted to value onv thegraduation 27, the plane determined by the axes wh c us s of the two collimators containin the test obmillimetres and, respectively,

'f'cross lines 32 and a double je'cts29and 30,31, 30', 31', to lie m horizontal 36 which it sees at agreat distance. 4-1

11 *ofjthe eye underjlexamination 12.

cornea ofthe icolli'mator lenses 9, they appear at an infinitely great distance an, Q

.vievvingm m cros cope that position which ly in the frontfocal plane of v the reversing consequently are maged inthe focal ,planeof the reflecting f surfaceof' the'cornea. The eye to be exan'v lined, 12, must1now begiven relatively to the 7 position. Theeye 12 views the luininous spot I reflectionby the surface of the These test objects-lying in the "focal planes 1 lens 20. In this plane therefore appear "also 2 images of the test 9bjects,1whereby the images reflected 1n the focal plane of the cornea serve ocular 1 6 must be sofdisplaced that the images. which the rotated in a guide (BS6126. reversing system 20, 21 produces of the test objects approximatelyinthe rear focal plane "of theflens21 coincidelwithgthe plane of the cross-lines 19. The observer may proceed also" in such a manner that, with the plane of the cross lines19' adjusted fixedly to the rear focal plane of'thelens 21, hefdisplaces the whole instrumentinthe direction of its axis untilhe cansee atxthe ocular 16 sharply,

imaging rayscan pass the lens 20 whic v have passed the aperture images lyin in the well discernible-place of the plane of the vertex. tangential. plane, whereas a 1 other imaging rays are stopped down. This procedure sin lesout that area of the cornea 11 upon w ich the examination is based and causes each oflthe apertures 23, 23", 23",

23" to be passed only bythe imaging rays of one of the'four test objects; the aperture 23, for example, is passed. only by the imaging rays of, thecro'ss' lines 32 on the surf face 8" of thelens' 6".' The refracting an-.

gles of the prisms 24,24, 24 and 24 covering the apertures 23, 23', 23 and 23' are so'chosen-that'the test object images projected b the reversing systems 20, 21 are so far 7 'dispiaced in the direction of the optical axls of the microscopethatthe images of each two opposite test objects, that is tosay the image of the cross lines 29 and the image.

of the crosslines 32 respectively cover on a cross 9 on theglass plate 18 the image of the? a tie scale 31, 31' and theimage of the dash escauaeey. lA s'withunaltered inclination of the collimator axesrelativeftofl the ,micrscope axisthe valuedepends only on the displacement of the images produced by the cornea, 11 from the elongation of the 7 optical axis of the micros'cope and this distance, in its turn, only on the corneal curvature, the displacement" resulting'in the case of an eye '12permits of arrivin at a certain conclusion as tothe value oft e radius of curvature of th'e corneall and, further, as

the refractive powerofthe cornea and the aqueous humour is 'rever'sely' proportional to this radius of curvature a conclusion canbe drawn from this. refractive power.' .Herefrom results the law for the divisionof the double'scales 31, 31 and 34, "34whose values can be found by" calculation or experimentally, whereby naturally the dimensions of. the instrument'must be considered." 3

f If the eye; under examination is axially symmetrical tlie observer will seefor instance the image illustrated by Figure :9. a A

characteristic featureof the said construction of the eye is thatthe Ion er lines of .thetest ob'ect's 29 and32 divi e' by halves the spaces tween theparallel lines 30, 30

and 33, 33 and the short lines indicate'the same values 'onthe two double scales 31, 31'

and '34,- 34. These values, are the sought 7 values of the radius of the corneal curvature and of the refractivepowenk Suppose that the principal section planes do not exactly coincide with the horizontal and the perpendicular plane throughthe microscopic axis, the observer will see in case of an eye afflicted with astigmatism-,-" 12, for instance the image illustrated by Fig'urelO.

This image is characterized by the fact that the long lines ofithe crosses 29 and 32 "do not lie in the centre of the space between the parallel lines 30, 30 and, respectively,

disposed on the observig 38, 33'. In order to providethi's coincidence the observer turns the instrument in the bearing 1 about its axis until at a certain turning angle to which the position of the principal section planes corresponds,: the

-alt)itudinal difi'erenceis compensated (Figure ;11 tion planesisindicatedby the index 28 on the. graduation 27 and the sought value of the N owthe position of the principal 'sec-' radii of curvature and the refraction values, which inthe case of astigmatic eye naturally are different in both principal section plane-sf =and'the imaging scale determined by the ob j ective '15. I claim: I 1 1' 1'. .An instrumentfor measuring'the curvature of the cornea, comprising an optical observing ,device, 'two collimatorjlenses, each collimatorv lens containing .in its focal plane a test object, the collimator lenses being so device that their axeslie in one plane with the axis of the ob- 7 serving instrument and" intersect this axis at. unchangeable angles approximately at one point, and a stop disposedin the observing device and having two apertures lying outside the axis of the observingvdevice in a plane containing this axis and the axes of thetwo collimators 2. An instrument for measuring the curvatureof the cornea, comprising an optical ob serving device, two collimator. lenses, ,each collimator lens containing in its focal plane a test object, the collimator lenses beingso disposed on the observing device that their axes lie in one plane withthe axis of the observing instrument and. intersect this axis at unchangeable angles. approximately at one point, a stop disposed in the observing device taining the axes of the twoitest objects, and at least one deviatin optical means inserted in one of the pathso partial rays.

'and having two apertures lying outsidethe I axis of the observing device in a plane con- 3."In an instrument according toclaim 1, v

the 'one test object having a scale at right an glesfto'the planedetermined by the two: test objects. and the axis of the observing device, and theother test object being an index.

; 14. In an instrument accordingto claim 1,

the one test object being a double scale at right angles to the plane determined by the two test objects and the axis of the observing device, index.

5. An instrument ture of the cornea, comprislng an optical observing device, this device comprising an objective, a system of reversing lenses provided behind the objective and an ocular, a means covering the aperture of the system of reversing lenses, this means having tWo apertures lying outside the axis of the said systemof reversing lenses andin a plane with this axis, and two test objects provided on the observing device in 'unchangeable position relatively to each other and to the axis of the observing device in the said plane.

6. An instrument for measuring the curvature of the cornea, comprising an optical oband the other test objectbeing an serving device,

for measuring the curva-.

this device comprising an objective, a system of reversing lenses provided behind the objective and an ocular, a means covering the aperture of the system of reversing lenses, this means having twoapertures lying outside the axis of the said system of reversing lenses and in a plane with this axis, two refractive Wedges each arranged in front of one of the two said apertures, and two test objects provided on the observing device in unchangeable position relatively to each other and to the axis of the observing device in the said plane.

7. In an instrument according to claim 5, a mark disposed in the focal plane of the ob jective.

Y HANS HARTINGER. 

